accessibilityIdentifierOrNull

This element's developer-set accessibilityIdentifier, or null — including when the identifier is present but blank, which is treated as absent rather than reported as a target (see the body for why, and for why it rejects without trimming).

Deliberately the only identity source Autograph reads off this tree. accessibilityLabel is user- facing text and is never read: UIKit gives no way to tell an explicit, developer-authored label apart from one Compose Multiplatform synthesizes from the element's displayed text, so falling back to it would silently defeat the "never capture displayed text" guarantee.

Why this needs two routes. In Objective-C every UIView carries accessibilityIdentifier — UIView adopts UIAccessibilityIdentification through a category. Kotlin/Native's cinterop does not model protocol conformance added that way, so UIView (and therefore UIButton, and every other UIKit control) is statically not a UIAccessibilityIdentificationProtocol and the cast below fails at runtime — measured, not inferred. The property is still there; only the binding's view of the type system is missing it, so it is reachable by asking the object itself.

The protocol cast alone was enough while the sole caller was autograph-compose, because Compose Multiplatform bridges its semantics as UIAccessibilityElement subclasses, which do conform in the headers. Aiming this at a UIKit/SwiftUI tree (#62) makes the gap load-bearing: a UIButton passes the clickability predicate and then yields no identifier, so every native tap is dropped and the pipeline is silently inert.

The fallback asks for the getter by selector, guarded by respondsToSelector, rather than trying and recovering: an Objective-C exception crossing back into Kotlin is not a catchable Kotlin exception, so a raise here takes the process down. The walk hands arbitrary objects to this function, so asking first is the only safe order — and once respondsToSelector says yes, performSelector cannot raise. (Key-value coding would reach the same property, but routes through valueForKey:, which an object is free to override and reject a key from; the selector call has no such surface.)